Field of the Invention
The present invention relates to an image pickup apparatus such as a digital camera, a control method therefor, and a storage medium, and in particular to improvements in a technique to control a photometric measurement operation of an image pickup apparatus such as a digital single-lens reflex camera having two photometric means.
Description of the Related Art
For image pickup apparatuses such as digital single-lens reflex cameras, a linear photometric sensor on which the number of pixels can be increased may be used in place of a logarithmic compression photometric sensor so as to perform a face detecting function, a subject tracking function, and so forth.
The linear photometric sensor, however, has a narrower dynamic range than that of a logarithmic compression photometric sensor, and hence there is a possibility that a subject brightness cannot be accurately measured by one photometric measurement operation. During photometric measurement using an image pickup device, for example, during Live View shooting or video shooting, the power to the photometric sensor is turned off so as to reduce power consumption, and when Live View shooting or video shooting is finished, the photometric sensor is started to perform photometric measurement. At this time, a plurality of photometric measurement operations suitable for a dynamic range of the photometric sensor is required, and hence the time required for the linear photometric sensor to perform photometric measurement is long.
Therefore, there has been proposed a technique to, for a digital single-lens reflex camera that has a photometric means capable of operating when a mirror mechanism has its mirror flipped down, and a photometric measurement means capable of operating when the mirror mechanism has its mirror flipped up, efficiently control photometric measurement operations of these two photometric means. According to this proposal, when the mirror mechanism has shifted from the state of having its mirror being flipped down to the state of having its mirror flipped up, a photometric measurement operation is performed by one photometric means based on a result of photometric measurement performed by the other photometric means (see Japanese Laid-Open Patent Publication (Kokai) No. 2006-163094).
The technique described in Japanese Laid-Open Patent Publication (Kokai) No. 2006-163094 above is useful when a logarithmic compression photometric sensor is used, but with this technique, an accurate photometric measurement value may not be obtained when a linear photometric sensor is used. This is because during Live View shooting, an image which is a simulated preview of exposure is displayed on a display unit, and accordingly, accumulation in an image pickup device may be done under photometric measurement conditions suited to camera settings (f-number, shutter speed, and ISO value), not photometric measurement conditions suited to a subject brightness.
For example, when Live View shooting is performed with camera settings according to which correct exposure is obtained in a dark part of a subject with a wide brightness distribution, accumulation in an image pickup device is performed over a wide range outside a dynamic range, and when an output from the image pickup device is out of the dynamic range, an accurate photometric measurement value cannot be calculated.
In this case, when a logarithmic compression photometric sensor is used, an accurate photometric measurement value can be obtained by one photometric measurement with a wide dynamic range being made use of even if information on photometric measurement performed by an image pickup device, which is not even close to a subject brightness, is handed over. However, a linear photometric measurement senor may not obtain an accurate photometric measurement value due to its narrow dynamic range even if information on photometric measurement performed by an image pickup device is handed over.